David Cameron, Nick Clegg and Ed Miliband have agreed to work together to tackle climate change, as they warned it posed a threat to national security and economic prosperity.
In what might be seen as a surprising move in the run-up to the general election, the three party leaders have pledged to work "across party lines" to agree cuts to the UK's carbon emissions.
They have also signed up to seeking a "fair, strong, legally binding" international climate deal, set to be negotiated in Paris at the end of the year, to limit global temperature rises to below 2C - the level beyond which "dangerous" climate change is expected.
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And they pledged to move to a low-carbon economy, ending the use of coal without technology to capture and store its emissions for power generation.
The statement signed by the Prime Minister, Deputy Prime Minister and the Leader of the Opposition said: "Climate change is one of the most serious threats facing the world today.
"It is not just a threat to the environment, but also to our national and global security, to poverty eradication and economic prosperity.
"Acting on climate change is also an opportunity for the UK to grow a stronger economy, which is more efficient and more resilient to the risks ahead. It is in our national interest to act and ensure that others act with us."
The statement comes after commentators have questioned political commitment on climate change and business leaders have called for certainty on carbon cuts, and in the face of entrenched disagreement on the issue in other key countries such as the US.
Former US vice president, Al Gore, said: "This agreement represents inspiring leadership and true statesmanship by all three men. The political courage it represents on all sides is exactly what our world most needs in order to solve the climate crisis."
And Paul Polman, chief executive of Unilever, said: "The importance of this pledge cannot be overstated.
"In this critical year, both for the international climate change negotiations and the agreement of the sustainable development goals, this statement of cross-party recognition of the importance of climate action, as well as support for a legally binding global deal, sets a terrific example for other countries to follow."
The three leaders have pledged:
::To seek a fair, strong, legally binding, global climate deal which limits temperature rises to below 2C.
:: To work together, across party lines, to agree carbon budgets in accordance with the Climate Change Act.
:: To accelerate the transition to a competitive, energy efficient low carbon economy and to end the use of unabated coal for power generation.